DC Current Indicator #4
The circuit below uses some common components to turn on an LED whenever DC current above a certain level is detected. The circuit uses a very popular LM393 dual voltage comparator from National Semiconductor and a common 1N4148 signal diode. The diode. . . Circuit by Dave Johnson P.E.-October, 2005

DC Current Indicator 6
The circuit below is a simple way to indicate when DC current is flowing through a wire. The circuit is designed so it will turn on a LED indicator light, whenever the voltage drop across a shunt resistor exceeds about 0.1volts. The value of the resist. . . Circuit by David A. Johnson P.E.-October, 2005

Detect Short Xenon Lamp Flashes
This circuit uses a small 2.5mm square photo diode in conjunction with a 100mH coil to detect the short light flashes from a xenon lamp. The coil makes the circuit immune to normal room lights. Its 10mv sensitivity can detect light flashes from a range of over 100 feet. . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002

Detect the narrow 1uS pulses
This circuit is designed to detect the narrow 1uS pulses produced by the above amplifier circuit. The clean logic type pulses produced by the discriminator are then sent to a frequency to voltage converter. The circuit is designed to process a pulse frequency. . . Circuit by Dave Johnson P.E.-March, 1999

Indicate DC Current Flow
The circuit below is a simple way to indicate when DC current is flowing through a wire. The circuit is designed so it will turn on a LED indicator light, whenever the voltage drop across a shunt resistor exceeds about 0.1volts. The value of the resist . . . Hobby Circuit designed by David A. Johnson P.E.-October, 2005

Indicates Battery Charge Current
This circuit turns on a LED whenever it detects at least 25ma of battery charge current . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Indicator for Acceptable Voltage
I have used this circuit many times in custom test fixtures where a simple go-no go indication was needed. The circuit can also be used to adjust a particular voltage be within specific high or low limits. The three LEDs will indicate if the voltage is . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2002

DC Current Indicator #4
The circuit below uses some common components to turn on an LED whenever DC current above a certain level is detected. The circuit uses a very popular LM393 dual voltage comparator from National Semiconductor and a common 1N4148 signal diode. The diode. . . Circuit by Dave Johnson P.E.-October, 2005

DC Current Indicator 6
The circuit below is a simple way to indicate when DC current is flowing through a wire. The circuit is designed so it will turn on a LED indicator light, whenever the voltage drop across a shunt resistor exceeds about 0.1volts. The value of the resist. . . Circuit by David A. Johnson P.E.-October, 2005

Design an Efficient Reset
1-May-03 EDN-Design Ideas When you work with microprocessors, you must ensure that when the power-supply voltage fluctuates to the minimum permissible level, VL, that the processor's ALU continues to operate normally. Also, when you switch on the power supply, the ALU must operate normally when the supply voltage equals or exceeds a certain high level, VH__ Circuit Design by Guillermo Bosque, Asesoría e Integracion de Tecnologías, Urduliz, Spain

Design low-duty-cycle timers
08/22/02 EDN-Design Ideas Designing astable circuits using the industry-standard 555 timer is a straightforward process when duty cycles are 50% or greater. However, you must overcome the many pitfalls of low-duty-cycle circuits to arrive at a desired result. Using only ideal components eases the design, but the components themselves are hard to obtain__ Circuit Design by Phil Rogers, Texas Instruments Inc, Rockwall, TX

Detect Short Xenon Lamp Flashes
This circuit uses a small 2.5mm square photo diode in conjunction with a 100mH coil to detect the short light flashes from a xenon lamp. The coil makes the circuit immune to normal room lights. Its 10mv sensitivity can detect light flashes from a range of over 100 feet. . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002

Detect the narrow 1uS pulses
This circuit is designed to detect the narrow 1uS pulses produced by the above amplifier circuit. The clean logic type pulses produced by the discriminator are then sent to a frequency to voltage converter. The circuit is designed to process a pulse frequency. . . Circuit by Dave Johnson P.E.-March, 1999

Digital Frequency Comparator
Here’s a digital frequency comparator for oscillators that indicates the result through a 7-segment display and a light-emitting diode (LED). When the frequency count of an oscillator is below ‘8,’ the...___ Electronics Projects for You

Double Dual Limit Window Comparator
This window comparator circuit has 4 limints, 2 lower limits and 2 upper limits, which can produce up to 4 separate outputs, each dedicated to a warning, an alarm or a control condition.___ Advanced Linear Devices, Inc

Dual comparator thermally protects lithium-Ion battery
18-Sep-03 EDN-Design Ideas Most manufacturers recommend that you don't change lithium-ion batteries at temperatures lower than 0°C or higher than 50°C. You can monitor both thresholds by adding a thermistor and dual(window] comparator to a lithium-ion battery charger(Figure 1). Set the low-temperature trip point at 2__ Circuit Design by Mike Hess, Maxim Integrated Products, Sunnyvale, CA

Dual Limit Microvolt Comparator
Low offset precision amplifiers make very accurate comparators. This is a window comparator when an output LED indicates that the input is outside of the window. Hysteresis to ensure smooth switching is provided to one of the offset nulling terminals with minimal impact on offset and therefore threshold accuracy. __ Linear Technology/Analog Devices App Note, Jun 21, 2011

Dual Output, Buffered Reference (On Single 3V Supply)
The amplifier configuration establishes the reference voltage across the 75k resistor. A fixed current is then forced into the 46.4k resistor and sets the lower output voltage. The upper voltage output is greater than the lower voltage output by the reference voltage. __ Linear Technology/Analog Devices App Note, Jun 21, 2011

Easy Method Calculates Comparator Trip Points
06/10/99 EDN-Design Ideas Using Millman's Theorem to calculate the resistor ratio reduces the time it takes to calculate the trip points on a comparator with hysteresis. This method eliminates lengthy computations and substitutions. Using this resistor ratio, you select two resistors, assign convenient values, and then calculate the third value__ Circuit Design by Virgil Lawrence, Micro Linear, San Jose, CA

Electronic fuse emulates fast- or slow-blow fuses
11/09/00 EDN-Design Ideas The electronic-fuse circuit in Figure 1 combines the properties of a current transducer and a solid-state relay to disconnect low power at preset levels. Using this circuit lets. PDF contains multiple circuits, scroll to find the one of interest__ Circuit Design by John A Hasse, Colorado State University, Fort Collins, CO

Expanded-scale indicator revisited
08/08/02 EDN-Design Ideas The visualization aid that a previous Design Ideas describes allows only the expansion of the upper end of the scale(Reference 1]. But what can you do if, according to your project requirements, you need to expand the middle region of the scale? Figure 1a illustrates the challenge. A voltmeter comprises a 100-µA dc meter and a series resistor__ Circuit Design by Abel Raynus, Armatron International Inc, Melrose, MA

Fast comparators find theIR niche in linear application
09/11/98 EDN Technical Article: Comparators don’t “just compare” in the same way that op amps don’t “just amplify. ” A collection of application circuits demonstrates just how flexible and useful a high-speed comparator can be.__ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke. He was 63.

Filter Allows Comparison Of Noisy Signals
02/06/03 EDN-Design Ideas When you need to compare the dc level of a noisy signal with a reference for further processing, the output of the comparator changes in a chaotic way when the dc level approaches that of the reference. You have a choice of two classic solutions to this problem One is to add hysteresis to the comparator, but, if the noise level is high, the hysteresis must be correspondingly high__ Circuit Design by Mario Milberg, CNEA, Buenos Aires, Argentina

Frequency comparator draws 8 mA
03/03/97 EDN-Design Ideas The circuit in Figure 1includes all the necessary components to build a simple, low-power frequency comparator. The circuit centers around the operation of IC1, which integrates an amplifier, a comparator, and a voltage reference.__ Circuit Design by Dalius Baranauskas, Semiconductor Physics Institute, Vilnius, Lithuania

Frequency comparator has status output
12/26/02 EDN-Design Ideas The original application for the circuit in Figure 1 was to check the number of revolutions of an engine with only one LED as an indicator. The measurement of the number of revolutions usually involves sensors with a frequency output proportional to the number of revolutions. The circuit compares the frequency output of such a sensor with a lower and upper limit and gives a visual result, usi__ Circuit Design by Susanne Nell, Breitenfurt, Austria

Frequency Comparer Produces Binary Result
09/29/94 EDN-Design Ideas Instead of resorting to full-blown frequency counters, the simple circuit in Fig 1 uses four ICs to rapidly compare the frequency of two pulse trains. The circuit produces a binary 0 if f1 is greater than f2 and a binary 1 if f1 is less than f2. The circuit exploits the fact that inevitably two consecutive leading edges of the higher frequency pulse train will follow each__ Circuit Design by Jay Kirschenbaum, Columbia University, New York, NY

Frequency Window Comparator has hysteresis
11/07/96 EDN-Design Ideas The frequency comparator in Figure 1 uses two VCOs. C1, R1+R2, and the voltage at pin 9 determine the frequency of IC1(900 Hz]. C3, R5+R6, and the voltage at pin 9 determine the frequency of IC2(1580 Hz]. If fIN is lower than 900 Hz, then the output P2 of phase-comparator 2 in IC1 is high and drives__ Circuit Design by W Dijkstra, Consultant, Waalre, The Netherlands

High Speed Comparator Techniques
AN13 The AN13 is an extensive discussion of the causes and cures of problems in very high speed comparator circuits. A separate applications section presents circuits, including a 0.025% accurate 1Hz to 30MHz V/F converter, a 200ns 0.01% sample-hold and a 10MHz fiber-optic receiver. Five appendices covering related topics complete this note. __ Linear Technology/Analog Devices

High-speed peak Detector uses ECL comparator
09/26/02 EDN-Design Ideas Professional electronics designers often use peak-detector circuit sin such applications as amplitude measurement, automatic gain control, and data regeneration. You can build a simple and fast peak detector from a serial diode and a shunt capacitor, but it suffers from serious inaccuracy that stems from the diode's forward-voltage drop__ Circuit Design by Przemyslaw Krehlik and Lukasz Sliwczynski, Institute of Electronics, Krakow, Poland

Indicate DC Current Flow
The circuit below is a simple way to indicate when DC current is flowing through a wire. The circuit is designed so it will turn on a LED indicator light, whenever the voltage drop across a shunt resistor exceeds about 0.1volts. The value of the resist . . . Hobby Circuit designed by David A. Johnson P.E.-October, 2005

Indicates Battery Charge Current
This circuit turns on a LED whenever it detects at least 25ma of battery charge current . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Indicator for Acceptable Voltage
I have used this circuit many times in custom test fixtures where a simple go-no go indication was needed. The circuit can also be used to adjust a particular voltage be within specific high or low limits. The three LEDs will indicate if the voltage is . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2002